Temporary directories ($TMPDIR)

In Linux the standard directory for temporary files is /tmp. For many applications this can be changed by setting the environment variable $TMPDIR. Specifying a suitable TMPDIR is an important optimization for programs that make a lot of scratch I/O.

Contents

• $TMPDIR in shell sessions and batch jobs
• Setting $TMPDIR for executing a single command with ssh

See also:

• Working with data
• Temporary/scratch files

$TMPDIR in shell sessions and batch jobs

On Hummel-2 directories for temporary files are automatically created and automatically deleted for every interactive session and every batch job. The names of these directories are generated in the Environment Module site/tmpdir and kept in these environment variables:

Variable	Explanation
$TMPDIR	This variable is always defined.
$RRZ_GLOBAL_TMPDIR	Scratch directory in /beegfs.
$RRZ_LOCAL_TMPDIR	Exists for Hummel-1 compatibility. Is set to /tmp.

Module site/tmpdir is automatically loaded in interactive session. In batch jobs it is loaded in:

source /sw/batch/init.[c]sh

Module site/tmpdir sets variables in the following way:

Environment	Settings
interactive session	TMPDIR=/beegfs/tmp/... RRZ_GLOBAL_TMPDIR=$TMPDIR RRZ_LOCAL_TMPDIR=$TMPDIR
batch job	RRZ_GLOBAL_TMPDIR=/beegfs/scratch/... RRZ_LOCAL_TMPDIR=/tmp TMPDIR=$RRZ_LOCAL_TMPDIR
interaktive batch job (salloc) without source /sw/batch/init.[c]sh	same as in interactive session (variables are inherited)
interaktive batch job (salloc) after source /sw/batch/init.[c]sh	TMPDIR=/beegfs/tmp/... (taken from session) RRZ_GLOBAL_TMPDIR=$TMPDIR RRZ_LOCAL_TMPDIR=/tmp

Setting $TMPDIR for executing a single command with ssh

Commands that are specified on the ssh command line do not run in the usual login environment. As a consequence $TMPDIR is not defined.

If, for example, the default directory for temprary files /tmp is too small, $TMPDIR can be created and defined this way:

• create a sub-directory in your SSD directory

    $ mkdir /places/$USER/ssd/tmpdir

• add these lines to your $HOME/.bashrc file

    if [[ -z $TMPDIR ]]
    then
        export TMPDIR=/places/$USER/ssd/tmpdir
    fi

Note that there is no automatic deletion here and that space used in this directory adds to your $SSD disk quota.